System for aligning receiver and transmitter circuits



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.N 4 NN IN1/Ewan JOHN P BYRNE ATT ORNEY Patented Aug. 17, 1948 SYSTEMFon ALIGNINGjRECEIvnR AND l l''IBANsMrrfrER craculfr's A1,011 F,Byrne,-Wel1esley Hills, .Mass., assignOl. ,t0

I .the United saresti Amer-ica as represented by I z the Secretary f WM'v I I* t Application May 23, 1945, SerialNo. '1595,'353" 1 claim.(orario- 113) The present invention relates in general to ceiverand atransmitter, thefoutput frequencylof which is determined by a variablefrequency Aoscillator which is common to.both receiver and transmitter.The .use of a common oscillator to determine the output frequency of thetransmitter makes it certain under `all conditions that the frquency ofthe transmitter is the same as that to which the receiver is tuned; thatis, the incoming signal frequency One of the advantages of the presentinvention is that an operator receiving signals on the receiver maytransmit a signal back to the sender merely by turning on the powercircuits of the transmitter without any further adjustment, since thecommon oscillator permits the simultaneous tuning of the receiver andtransmitter to a single frequency.

The range of frequencies that can be covered by a receiver ortransmitter having single tuning circuits in which a desirablesensitivity in the case of a receiver, and effective transmitting rangein the case of a transmitter are maintained, is limited by practicalconsiderations in the design of their circuits. Accordingly, in thepresent invention when it is desired to cover a broad range offrequencies, there are provided separate tank circuits for several bandsof frequencies within the entire range covered. The common oscillator isdesigned to be tunable over a band greater than the width of the bandcovered by the individual tank circuits.

Other objects, features and advantages of this invention will suggestthemselves to those skilled in the art and will become apparent from thefollowing description of the invention taken in connection with theaccompanying drawing which is a block diagram showing the preferredembodirnent of the invention.

Incoming signals are received on the receiving antenna, lil and passedthrough one of the receiver tank circuits II which has been chosen bythe operator as the tank circuit proper to cover the band of frequenciesin which the received signal is found. The selection of the proper tankcirceived signal is found. The selection of the proper tank circuit ismade by switches I2 and I3. The signal then passes into the mixersection I4 of the receiver Where it is combined with oscillationsproduced by thetunable oscillator I5, resulting in an intermediatefrequency which in the remaining parts IB of the receiver is amplifiedand detected.. inY anconvlentional manner.. @.{I'heA oscil- .later el 5.istunab1efmar1ual1y over a bander frequencies-whichqis greater in widththan the band of ffrequenciesacovered by fthe tank .circuits A ,B, C,vandfD,q;gener,ally designated as II.

Itis contemplated;wandering-the creratlfof the receiver all of the circof ,thetransrnitter will .be energized with-the lpossibl-e "exception ofthe final.powerzconsuminsylead.-Ci ts Sechi-as the antenna and tan-kcircuits. e, ,the .switch Il open n-o oscillations are lfed into thetransmitter from the oscillator; therefore, no energy can be radiatedfrom the transmitter antenna 2U. However, all the circuits of thetransmitter are tuned and put into condition so that when the switch Ilis closed the transmitter will transmit a wave of the same frequency asthat to which the receiver is tuned. This is accomplished as follows:The frequency to which the transmitter in termediate frequency circuits2l are tuned is the same as that to which the receiver intermediatefrequency amplifier circuits are tuned. The result is that whenoscillations from this amplifier 2! are mixed with oscillations fromtheoscillator I5 in the transmitter mixer 22, signals of the differencefrequencies are introduced into one of the transmitter tank circuits 23.A transmitter tank circuit covering the same band of frequencies as thatcovered by the receiver tank circuit, which is connected in thereceiver, is chosen and connected into the circuit by means of theswitches 2li and 25. Switch 24 is mechanically linked by any well knownmeans, shown diagrammatically as 2B, to the switch I3, and switch 25 issimilarly linked by 21 to switch I2. Likewise, the two sets of switchesoperate simultaneously by means of a mechanical linkage 28.

It is well known that if -two frequencies, A and B, are mixed inaccordance with the superheterodyne principle that there aretworesulting frequencies, A+B and A-B. It is common practice to choosein a receiver the A-B frequency for' further amplification and detectionand to include means in a receiver for rejecting the A+B,

' or image, frequency. In the arrangement of the present invention,since the intermediate frequency of the transmitter and receiver are thesaine, it is desired in the transmitter mixer 22 to select the A+Bfrequency in order to have the output yof that section be of the samefrequency as the frequency of the signal being received by the receiver.Accordingly, filter means are provided in the transmitter mixer Z2toremove the A-B frequency, which in that case becomes the imagefrequency. Such means are well known .Y 3 i and may be of conventionaldesign; therefore, no description of them is needed in .this presen-tspecifica/tion.

While there has been here described what is at present considered to bethe preferred embodiment of the invention, it Will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the scope of the invention.

What is claimed is:

mon oscillator, a mixer stage connected to re-A l v A radio signalsystem comprising a receivercira cuit, a transmitter circuit and atunableoscil-y oscillator, a mixer stage connected to receive the outputof said signal oscillator, said amplifier and modulator means and saidcommon oscillator to produce a signal representing the sum frequency ofthe intermediate frequency and the oscillator frequency, means .tosuppress the dierence frequency representing the'dierence between thecommon oscillator frequency and the intermediate frequency, a pluralityof band pass radio frequency circuits, each designed to cover thesame'vband of frequencies covered by the band f' pass v`circuits inthereceiver, and common means celve the output of said radio frequencycircuits and the output of said common oscillator to pro-l duce anintermediate frequency representing the difference frequency between areceived frequency and the common oscillator1 frequency, means tosuppress the frequency which is the sum frequency of the receivedfrequency and the common oscillator frequency, and means lto amplify anddetect the intermediate frequency? said transmitter circuit comprisingan oscillator to produce a sign-al having a, frequency equal to theintermediate frequency produced in the receiver circuit, means toamplify said signal and means to modulate said-signal, .the aforesaidcommon for selecting in the receiver circuit and in the transmitterAcircuit matched band pass circuits whereby said transmitter is alwaystuned to the same frequency as said receiver input circuits.

JOHN F. BYRNE.

REFERENCES CITED The `following references are of record in the ille ofthis patent:

UNITED STATES PATENTS l n -Date 2,408,826 V-Ogel Q Oct. 8, 1946

